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Commit 029e7622 authored by Larry Bassel's avatar Larry Bassel
Browse files

arm64: implement CONFIG_STRICT_MEMORY_RWX for arm64 



In order to improve security, protect the sections
the kernel uses for the 1-to-1 mapping of memory
as strictly as possible (i.e. no writing on text,
executing data, etc.)

Change-Id: I6ef6837502b8af4f914512f95ff902276e191351
Signed-off-by: default avatarLarry Bassel <lbassel@codeaurora.org>
parent 72bd72cf

arch/arm64/kernel/entry.S

+9 −0
Original line number Diff line number Diff line
@@ -139,7 +139,12 @@ tsk .req x28 // current thread_info 
 * Interrupt handling.

 */

	.macro	irq_handler

#ifdef CONFIG_STRICT_MEMORY_RWX

	ldr	x1, =handle_arch_irq

	ldr	x1, [x1]

#else

	ldr	x1, handle_arch_irq

#endif

	mov	x0, sp

	blr	x1

	.endm
@@ -676,5 +681,9 @@ ENTRY(sys_rt_sigreturn_wrapper) 
	b	sys_rt_sigreturn

ENDPROC(sys_rt_sigreturn_wrapper)



#ifdef CONFIG_STRICT_MEMORY_RWX

.data

#endif



ENTRY(handle_arch_irq)

	.quad	0

arch/arm64/kernel/head.S

+4 −0
Original line number Diff line number Diff line
@@ -207,7 +207,11 @@ CPU_LE( movk x0, #0x30d0, lsl #16 ) // Clear EE and E0E on LE systems 
	msr	vttbr_el2, xzr



	/* Hypervisor stub */

#ifndef CONFIG_STRICT_MEMORY_RWX

	adr	x0, __hyp_stub_vectors

#else

	ldr	x0, =__hyp_stub_vectors

#endif

	msr	vbar_el2, x0



	/* spsr */

arch/arm64/kernel/vmlinux.lds.S

+18 −0
Original line number Diff line number Diff line
@@ -8,6 +8,9 @@ 
#include <asm/thread_info.h>

#include <asm/memory.h>

#include <asm/page.h>

#ifdef CONFIG_STRICT_MEMORY_RWX

#include <asm/pgtable.h>

#endif



#define ARM_EXIT_KEEP(x)

#define ARM_EXIT_DISCARD(x)	x
@@ -52,6 +55,9 @@ SECTIONS 
		_text = .;

		HEAD_TEXT

	}

#ifdef CONFIG_STRICT_MEMORY_RWX

	. = ALIGN(1<<SECTION_SHIFT);

#endif

	.text : {			/* Real text segment		*/

		_stext = .;		/* Text and read-only data	*/

			__exception_text_start = .;
@@ -68,19 +74,31 @@ SECTIONS 
		*(.got)			/* Global offset table		*/

	}



#ifdef CONFIG_STRICT_MEMORY_RWX

	. = ALIGN(1<<SECTION_SHIFT);

#endif

	RO_DATA(PAGE_SIZE)

	EXCEPTION_TABLE(8)

	NOTES

	_etext = .;			/* End of text and rodata section */



#ifdef CONFIG_STRICT_MEMORY_RWX

	. = ALIGN(1<<SECTION_SHIFT);

#else

	. = ALIGN(PAGE_SIZE);

#endif

	__init_begin = .;



	INIT_TEXT_SECTION(8)

	.exit.text : {

		ARM_EXIT_KEEP(EXIT_TEXT)

	}

#ifdef CONFIG_STRICT_MEMORY_RWX

	. = ALIGN(1<<SECTION_SHIFT);

	__init_data_begin = .;

#else

	. = ALIGN(16);

#endif

	.init.data : {

		INIT_DATA

		INIT_SETUP(16)

arch/arm64/mm/init.c

+10 −0
Original line number Diff line number Diff line
@@ -343,11 +343,21 @@ void __init mem_init(void) 
	}

}



#ifdef CONFIG_STRICT_MEMORY_RWX

void free_initmem(void)

{

	poison_init_mem(__init_data_begin, __init_end - __init_data_begin);

	free_reserved_area(PAGE_ALIGN((unsigned long)&__init_data_begin),

				  ((unsigned long)&__init_end) & PAGE_MASK,

				  0, "unused kernel");

}

#else

void free_initmem(void)

{

	poison_init_mem(__init_begin, __init_end - __init_begin);

	free_initmem_default(0);

}

#endif



#ifdef CONFIG_BLK_DEV_INITRD

arch/arm64/mm/mmu.c

+22 −1
Original line number Diff line number Diff line
@@ -185,6 +185,26 @@ static void __init alloc_init_pte(pmd_t *pmd, unsigned long addr, 
	} while (pte++, addr += PAGE_SIZE, addr != end);

}



#ifdef CONFIG_STRICT_MEMORY_RWX

pmdval_t get_pmd_prot_sect_kernel(unsigned long addr)

{

	if (addr >= (unsigned long)__init_data_begin)

		return prot_sect_kernel | PMD_SECT_PXN;

	if (addr >= (unsigned long)__init_begin)

		return prot_sect_kernel | PMD_SECT_RDONLY;

	if (addr >= (unsigned long)__start_rodata)

		return prot_sect_kernel | PMD_SECT_RDONLY | PMD_SECT_PXN;

	if (addr >= (unsigned long)_stext)

		return prot_sect_kernel | PMD_SECT_RDONLY;

	return prot_sect_kernel | PMD_SECT_PXN;

}

#else

pmdval_t get_pmd_prot_sect_kernel(unsigned long addr)

{

	return prot_sect_kernel;

}

#endif



static void __init alloc_init_pmd(pud_t *pud, unsigned long addr,

				  unsigned long end, phys_addr_t phys)

{
@@ -204,7 +224,8 @@ static void __init alloc_init_pmd(pud_t *pud, unsigned long addr, 
		next = pmd_addr_end(addr, end);

		/* try section mapping first */

		if (((addr | next | phys) & ~SECTION_MASK) == 0)

			set_pmd(pmd, __pmd(phys | prot_sect_kernel));

			set_pmd(pmd,

				__pmd(phys | get_pmd_prot_sect_kernel(addr)));

		else

			alloc_init_pte(pmd, addr, next, __phys_to_pfn(phys));

		phys += next - addr;